Upon passing their scrutiny (δοκιμασία), the new Councilors swore the so-called “Bouleutic Oath.” According to Aristotle, this practice dated back to the eighth year after Cleisthenes established the democracy, or 501/500 BCE (Aristot. Ath. Pol. 22.2; source for date, Rhodes, Commentary on the Aristotelian Athenaion Politeia [Oxford, 1993] 262).

There is no single literary text or inscription that records the oath that the Councilors (βουλτεῦται) swore, but we can reconstruct it from scattered comments and references in different texts and inscriptions. It is important to remember, however, that these sources are from different dates, some from the 5th century (Lysias), some from the early 4th century (Xenophon), and some from the later 4th century BCE (Demosthenes). It is unlikely that the oath remained the same in wording and content over the course of 200 years. Nevertheless, the evidence we have does give us a picture of how the Athenians both empowered, and limited the power of, the Council.

A fragmentary quotation from the ancient historian Philochorus adds to our list of clauses in the Bouleutic Oath: “And the Council at that time began for the first time to sit according to letters; and even now they swear to sit in the letter to which they have been randomly assigned” (καὶἡβουλὴκατὰγράμματότεπρῶτονἐκαθέζετο·καὶἔτινῦνὀμνῦσινἀπ’ἐκείνουκαθεδεῖσθαιἐντῶιγράμματιὧιἂνλάχωσιν) (Philoch. 328 F 140; quoted in a scholion, or marginal note, to Aristoph. Pl. 972). This “sitting by letters” seems to mean that Councilors were assigned seats for their meetings, and they swore to sit only in their assigned seats. This might have been intended to prevent factions from forming within the Council, as might happen if all of the Councilors from one deme sat together when the whole body met.

A speech by Demosthenes quotes portions of a different oath, the one sworn by jurors in the People’s Court. These jurors swore, among other things, that “I am not less than thirty years old” (γέγοναοὐκἔλαττονἢτριάκονταἔτη) (Dem. 24.151). Since Xenophon tells us that Councilors also had to be at least thirty years old (Xen. Mem. 1.2.35), it is possible that Councilors likewise swore that they met the age requirement. On the other hand, as P.J. Rhodes has pointed out, such an oath might not have been necessary once each candidate for the Council had undergone scrutiny (see P.J. Rhodes, The Athenian Boule [Oxford, 1972] 195).